Hey! Author from the paper here! Nanomaterial coatings are applied to the sponges (and could be applied to other membranes, filters, or adsorbents as well) to

Hey! Author from the paper here! Nanomaterial coatings are applied to the sponges (and could be applied to other membranes, filters, or adsorbents as well) to tailor their surfaces for the adsorption of particular metal ions. These nanomaterials physisorb metal ions with high capacity and specificity due to high surface area and abundant surface sites for adsorption (and desorption for regeneration under acidic conditions).